Kathleen Miller, Wisconsin, University of Wisconsin-Madison, Madison, WI and William F. Tracy, 1575 Linden Dr., University of Wisconsin-Madison, Madison, WI
There are three main endosperm genotypes for commercial sweet corn varieties: sugary (su1), sugary enhancer (su1se1), and supersweet (sh2). The “sugary enhancer” genotype is a double mutant su1/su1, se1/se1 and has been one of the most widely grown endosperm types in fresh market production, creating corn with tender kernels and lasting sweetness. (Tracy, 2001). Sugary enhancer quality has been attributed to texture, flavor, sweetness, and pericarp of sweet corn (Ferguson et al. 1978). However, inconsistencies in sugar and starch accumulation indicate other factors contribute to sugary enhancer quality. With recent fine mapping of the se1 gene, we have developed populations to determine the specific function of se1 in the starch synthesis pathway. Knowing the location of se1 helps isolate it from possible modifier loci involved in high quality corn. We developed two F5 recombinant inbred line (RIL) populations from parental crosses of divergent sweetness, one heterozygous for se1 and one homozygous. The linkage map was developed using a genotyping by sequencing (GBS) method with 20,000 single nucleotide polymorphism (SNP) markers. With this map, novel quantitative trait loci (QTL) were found to influence sugar and starch content. A new predictive platform using NIRS was developed to measure starch, amylose, amylopectin, phytoglycogen, total sugar, sucrose, fructose, glucose, and maltose at the fresh eating stage and at the dry harvest stage. This was validated with 15% random subsample using wet lab techniques and has a predictive ability with a high R2.